Various synthetic latices have heretofore been commonly used for bonding together filaments or fibers of nonwoven fabrics to form durable industrial wipes or toweling. Such compositions must meet a number of technical and practical requirements. In particular, the latex composition, after having been applied to a nonwoven cellulosic based substrate and subsequently dried, should produce a fabric which is soft, flexible, and nonabrasive, and which has good tensile strength when wetted by water or various solvents.
It is preferred that the latex compositions used as binders for nonwoven cellulosic based substrates should not cause undesirable discoloration or yellowing of the fabric. It is also preferred that such compositions exhibit good long-term colloidal stability and good mechanical stability under high shear to avoid excessive build-up of latex particles on spray nozzles used for applying the latex to the substrate.
Known synthetic latices suitable for binding the fibers of nonwoven substrates include aqueous emulsions of multicomponent copolymers comprised primarily of styrene and butadiene. With such conventional prior art compositions, it has generally been necessary to utilize high amounts of melamine formaldehyde resins and/or high amounts of N-methylolacrylamide monomers.
A disadvantage with such compositions is that they contain or generate relatively high amounts of free formaldehyde which is now regarded as being highly undesirable from an environmental standpoint.
Accordingly, it would be highly desirable to provide an inexpensive latex binder capable of achieving high wet tear strength while reducing the need for melamine formaldehyde resins and/or N-methylolacrylamide monomers.